Models for Estimating Reference Evapotranspiration in Different Periods in Rio Verde, Goiás, Brazil

The water management in irrigated agriculture begins determining the need of water for the culture. Therefore, it was intended to evaluate the performance of the models of estimation reference of evapotranspiration (ETo) with regard to the method Penman-Monteith (PM), standard method, for Brazilian Cerrado Region (tropical grassland/savannah). The climate elements were obtained from the conventional weather station of Rio Verde from January/1972 to December/2016. It was compared the performance of the daily average ETo, during the dry, rainy and annual periods, by the PM method with regard to another 26 methods. Through the coefficient of determination, it was verified the methods of Turc (T) and Radiation-Temperature (RT) approached more to the PM, at any time of the year, being able to replace the standard method. The ETo average in the annual period was 3.8 mm day-1, for the dry period due to the smallest amount of solar radiation, the period submitted lower levels of ETo. The other models in which were used fewer amounts of climate data, they overestimated or underestimated the PM model by up to 57.9% and 60.7% respectively. With the management of water in agriculture, water availability can be increased in the hydric bodies, characterizing it as a tool for water management with the rational use of water resources.